USP s/n using blank injection not calculating for all peaks

I am trying to calculation s/n by using the blank injection noise. The Blank column is checked for the blank injection in the sample set(which is the 1st injection) and the following are enabled in the Suitability tab in the processing method:
-Calculate Suitability Results
-Calculate Suitability Results for Unknown Peaks
-Void Volume: 1.000
-US Pharmacopoeia
-Calculate USP, EP, JP s/n
-User noise centered on peak region in blank injection
-HH Multiplier for USP s/n: 20

For this method there are lots of small peaks, some are identified as Components in the PM, some are unknowns not identified. Empower is only calculating the USP s/n field result for some of the peaks and I cannot find a correlation as to why, it seems random. Empower is not even giving me the USP s/n for all the named components from the PM and then only some of the unknowns. It doesn't seem to be connected to the Int Type (BB, VV, etc) either. 


  • MarcNoble
    edited December 2022
    Hi Mlespake,

    I am no expert on System Suitability and S/N but I do know that there needs to be a minimum number of points between segments for S/N to be calculated.  WKB48599.  Any chance that is what is causing your "random" result?

    There is a ton of other info in the KB on S/N, maybe there is a gem in there for you.  Use this link.

    Good luck!